Electric motor



L. L. 0000s.

ELECTRIC MOTOR. APPHCATlO N FILED JUNEZG, 1920.

7 1,405,502, 7 Patented Feb. 7, 1922.

I N VEN TOR.

UNITED STATES PAT ENT OFFICE.

LEE L. DODDS, 0F BROOKLYN, NEN YORK.

ELECTRIC Moron.

To all whom it may concern:

Be it known that 1, LEE L. Donne, a citizen of the United States, residing at Brooklyn, in'the county of Kings and State of New York, have invented certain new anduseful Improvements in Electric lllotors, of which the following is a full, clear, and exact description.

This invention relates to electric motors and particularly to types adapted to intermittent or step-by-step movements such as are employed for example, in driving 'secondary clocks, tickers, or small apparatus and controlled by a master mechanism. An object of my invention is to provide an improved motor which has a very short air gap in its magnetic circuit and is susceptible of a step-by-step operation, which will not overrun its increment of movement, and which will be controlled with certainty by the master mechanism.

A further object is to provide a motor of: this type which is simple, compact and inexpensive, and durable, eflicient, and reliable in operation. Other objects and advantages will be apparent from the following description and the novel features of my invention will be particularly pointed out in claims.

In the drawings:

Fig. 1 is a plan of a simple motor which has been constructed in accordance with my invention, and

Fig. 2 is a sectional elevation of the same, taken substantially along the line 2 2 of Fig. l.

In the illustrated and preferred embodiment, 1 provide a bolt-shaped permanent magnet 1 for supplying a continuous magnetic field. An armature 2 havinga longitudinally slotted periphery is carried by a shaft 3 which is rotatably carried by the stein & oi the magnet 1 with the armature across the end of the stem, and rotating in a plane transverse thereto. A series of pole pieces 5 of soft iron are carried by the head plate 6 of the magnet'l in spaced relation around the stem i and parallel thereto. A bearing plate T of brass is secured to the outer face of each pole, piece 5 at the upper end thereof. A. secondary armature S is pivoted to each bearing plate T at pivot 9, the armature 8 being slightly spaced from and disposed along a side face of its pole piece but movable toward and iromthe same. A strip 7 Specification of Letters Patent. Patented Feb, 7, 192 2;

1920. Serial No. 391,923.

substantially radial with respect to the armature 2, with its inner end just clearing the projections 10 formed in the arma-f ture 2 by the slots in its periphery. A spring ll 'reacts between an extension 12 of the armature 8 and brass anchor bracket 13 of the pole piece 5 to normally hold the secondary armature away from its ole piece, the secondary armature being limited in movement in this direction by any suitable adjustable stop 14. Surrounding the pole pieces 5 are electro-m'agnet coils 15 and 16. The electro-magnets are connected in series, parallel, or series-parallel with the line wires 17 and 18. In the illustrated embod-iment the series parallel is employed for convenience, in which each electromagnet coil 15 is connected in series with an adjacent electro-magnet coil 16. The line wires 17 and 18 are connected to a source of alternating current and I may eonveniently secure such a current by connecting the wires 17 and 18 through a reversing switch 19 to direct current line wires 20 and 21, the operation of the switch producing the alternations in the direction of current flow. Any source of alternating current having the desired frequency may be employed however.

Electromagnet coils 15 are either wound or connected to the line wires so that the current therein will pass in a direction opposite from that of the other electromagnetcoil (16), whereby when all the coils are energized a magnetic field will be set up by each, the lines of force of each set of which will pass in opposite directions in alternate cores 5.

Assuming that the upper end of stem 4 of the permanent magnet is a N pole, each projection 10 will have the same polarity, and the upper ends of the cores 5 would normally all be S poles. lVith' the current passing in one direction through the line wires 17 and 18, the upper ends of the coils '15 would represent S poles due to the magnetic field set up by the passage of current in one direction through the coils, and this field would amplity that of the permanent magnet which passed through the cores 5 of these coils to produce similar polarity. Since the polarity of the upper ends of the cores of these coils prevents direct contact of the armature 8 is different from that of the armature projections, a strong pull between the two will take place tending to rotate the armature and bring the projectionsthereof which are nearestto the cores of coils 15 nearer thereto and shorten the air gap. The other coils 16 simultaneouslyset up in their cores a magneticfiel'd which is opposed or counter to that of the permanent magnet which normally passes through the same, so that one field neutralizes or counteracts the effect of the otherand no material .pullbetween the 3 cores, of-fthese magnets and the armature projections will, take place. The armature will be rotated until the 'air gap betweenthe cores of coils-15 and the nearest armature projection is shortened as much as possible whereupon'it-wiljl be brought to, rest and held in that position. ;This movement brings other projections 10 adjacent to but displaced fromthe cores of the other coils 16. Itnow the direction of current in the line wires '17 and18is reversed by the reversing switch 19, the coils 15 will, set up the opposed or counter-magnetic fieldand render their-cores ineffective uponthe armature 2 and coils 16 willset-up the amplifying field. This change isdue to the fact thatthe currentpasses-through coils 15 and 16in opposite directions, and reversal of current I the armatureadj acent to but-displaced from the upper ends of the cores of coils 15 so that upon another reversal of current, the coils 15 will again become effective to amplify the permanent field and cause further rotation of the armaturein the same di- :line wires 17 and 18.

rection. This will continue step-bystep during thereversals of current flow in the V The operation has been described thus far as thoughthe secondary armatures -8 were inactive, since in the broadest aspects ofthis invention, they are in effect butcxtensions of'the cores 5. and the motor would be operable if they were stationary. When the coils -15 amplifythe permanent field, this field passes through the cores, the secondary armature extensions 8'a-nd the nearest proj ections 10 of the armature 2. The tendency of the lines of force is to shorten the air gaps; and thus the torque of this field will pull each active secondary armature toward itspol-e piece and also rotate the armature 2 to bring the projections 10 which are then nearest to the active secondary armatures nearer thereto and substantially into alignment with the free ends of the latter. Overrunning of the armature 2 will beprevented by this torque, and the rotary armature will 7 7 thus be controlled with certainty.

The supports 7 ofthe secondary armatures must be of brass or similar non-magnetic material, because if iron were used the lines of force would pass'from the cores through the supports to the secondary armature instead of through thegap 'which provides the torque or-pull. A similar operation occurs when the coils .16 are ener gizedto amplify the permanent field and the coils 15 have the counter field. When the coils are connected: to set up'the counter or opposing field theireffect upon their secondary armatures is niland the latter will be shifted away from their cores by the springs 11. 'A spring pawl 22 may be carried by the stationary parts and engage with the projections'of the armature to prevent retrograde movement of the latter, but inasmuch as Icontemplate having the cur rent constantly passing in one "direction or the other, the pawl is superfluous and will. not ordinarily be employed. The secondary armatures providefor a greater stroke or increment of movement of the rotary armature with a much shorter air gap than would be possible without them, and the efficiency 7 and certainty of operation of the motor is accordingly increased. If the reversals of current stop, the motor will likewise stop. The period or interval between the reversals can be varied as desiredfandrmaybe accomplishedby any suitable mechanism. In-

the illustrated embodiment I have illustrated four coils, but the number can be increased or decreased as desired, or the increment of movement varied by varying the pitch of the teeth or projectionsof the armature and the I extent of movement of the secondary armatures.v

The effect of the opposing and amplifying fields upon the continuous field of the permanent magnet is substantially that of a field which shifts progressively in a circular direction about the armature, and if the number of coils be increased with a consequently closer angular spacing the progressively shifting field effect is more marked.

I have illustrated and describeda perma-' nent magnet as the source ot the continuous field for polarizing the rotary armature and the T-shaped standard, but this is illustrative only of a simple embodiment,since obviously an electro-magnetic COll connected to a constant source of direct current would maintain the continuous field andbeinevery way the equivalent of the permanent mag net. It is also obvious'that various other changes in the details illustrated and described may be madewithin the principle and scope of my invention.

an armature mounted for limited pivotal movement adjacent each temporary magnet to be operated thereby, a driven armature mounted adjacent the permanent magnet to be magnetized thereby and movable relative thereto, also toward and with the active first mentioned armatures, and means for progressively demagnetizing certain of said tem porary magnets to render their corresponding armatures ineffective and additionally magnetizing other of them, the magnetic action between the additionally magnetized temporary magnets and other armatures and the driven armature producing relative movement between them.

8. An electric'motor, comprising a permanent magnet for supplying a continuous magnetic field, a main armature adapted to be continuously magnetized with a certain polarity by said field, pole pieces extending from the magnet, arranged around the armature, and each having a normal. polarity different from that of the armature, a secondary armature mounted for movement toward and from each pole piece, means for progressively counteracting the magnetism in certain of the pole pieces and their armatures to permit of a magnetic torque between the secondary armaturesof the other pole pieces and those pole pieces and also between those secondary armatures and the main armature, and spring means normally holding the secondary armatures away from their pole pieces.

4:. An electric motor comprising a rotatable armature having a series of spaced projections thereon, pole pieces adjacent the armature and disposed around the same, a secondary armature pivotally carried by each pole piece and extending in a direction radial to the armature with an end just clearing the projections of the rotary arma ture when against the pole piece, a spring normally holding the secondary armature slightly out of radial position, means for causing a magnetic field to pass successively through certain of the pole pieces and secondary armatures to exertapull between the same and projections of the rotary armature and move the effective secondary armatures toward their pole piece and also exert a torque upon the rotary armature to rotate it and bring projections substantially into alignment with the ends of the effective secondary armatures. I

5. An electric motor comprising a rotary armature having spaced radial projections on its periphery, apole piece, a secondary armature pivotally carried by said pole piece for movement toward and from the same with an end moving adjacent to but clearing. the projections of the rotary arma ture, a spring for normally holding the sec ondary armature away from the pole piece, and means for intermittently causing a magnetic field to pass through the pole piece, seceondary armature and the rotary armature projection then nearest to the end of secondary armature for moving the said projection adjacent to the end of the secondary armature and also both together until the secondary armature completes its stroke toward the pole piece.

6. An electric motor comprising a rotary armature having spaced radial projections on its periphery, a pole piece, a secondary armature pivoted to said pole piece for movement toward and from the same, with 95 an end moving adjacent to but clearing the projections of the rotary armature, a

spring for normally holding the sec ondary armature away from the pole piece, and means for normally supplying a continuous magnetic field through the pole piece, secondary armature and the rotary armature projection then nearest to the end of the secondary armature for moving the said projection until it is adjacent to the end of the secondary armature and also both together until the secondary armature completes its stroke toward the pole piece, and means for intermittently setting up a, counter-magnetic field to permit of retraction of the secondary armature by the spring.

7. An electric motor comprising a rotary armature having spaced radial projections on its periphery, a pole piece, a non-magnetic support carried by the pole piece, a secondary armature pivoted to the support and slightly spaced from, but movable toward and from the pole piece, means for normally supplying a continuous magnetic field through the pole piece, secondary armature and me rotary armature projection then nearest to the end of the secondary armature for moving the said projection until it is adjacent to the end of the secondary armature and also both together until the secondary armature completes its stroke toward the pole piece and means for intermittently setting up a countermagnetic field to permit of retractionof the secondary armature by the spring. 13 0 v r r 1,405,502 r V .8. An electric motor comprising a moving main armature and for causing movement 10 main armature, having spaced projections of the same together to the extent of the sand thereon, a plurality of secondary armatures limited movement, and means foryieldingly magnetic attraction between the secondary my signatureharranged along the direction of the path of holding the secondary armatures at the other movement of the projections'of the main extreme of their movement when not subarmature and mounted for limited movejectedto the said magnetic attraction. 15

ment in that direction, means for causing In Witness whereof, I hereunto'subscribe armatnres and adjacent projections of the V L. DODDSQ 

